1. Field of the Invention
The present invention relates generally to a device for producing precise incremental joint movement in a patient, and more specifically to a device for selectively producing precise temporalmandibular joint movement in a patient in either of two opposite directions, wherein the device is operated by the patient during the making of internal images of the joint by magnetic resonance imaging.
2. Description of Related Art
It is known to diagnose various disorders, such as joint pain, by viewing internal images of the area under investigation at stepped positions. Such investigations can be performed by standard x-rays, by the new CT scan or by the even newer technique of magnetic resonance imaging (MRI).
For example, patients may suffer from a temporalmandibular joint (TMJ) disorder in which opening or closing of the lower jaw can be accomplished, if at all, only with severe pain or discomfort. Treating of these patients involves personal observation by a physician, the accuracy of which can be significantly enhanced with the aid of a series of internal images made of the jaw area at spaced stages of jaw opening through MRI techniques.
In the past, the progressive opening of the temporalmandibular joint for the above diagnosis has been accomplished by the physician or a technician inserting a wedge-type dental block between the patient's jaw bones (i.e., teeth) and forcing the block rearward in "slow" incremental steps. A scissors-like forceps, having a releasable pawl mechanism for locking the forceps in each stage of jaw opening, also has been used.
However, the foregoing procedures have a number of disadvantages. For example, the use of the manually inserted, wedge-type dental block is relatively inaccurate and requires the presence of a physician or technician with the patient during the insertion procedure. The scissors-like forceps, while more accurate, is cumbersome and unwieldy, and still requires great care in order to achieve evenly spaced steps. Prior art devices also usually comprise at least some magnetic material and, therefore, are not suitable for magnetic resonance imaging.
To overcome the shortcomings of the prior art, U.S. patent application Ser. No. 07/019,459, filed Feb. 26, 1987, now U.S. Pat. No. 4,834,112, of which this application is a continuation-in-part and which is assigned to the same Assignee as this application, discloses a precise device for producing incremental joint movement in a patient, which contains no materials with magnetic properties and which, therefore, is suited for use in magnetic resonance imaging. This device accomplishes temporalmandibular joint incrementing in a magnetic resonance imaging procedure precisely and simply, and may be patient-operated so as to not require the immediate presence of a physician or technician with the patient. However, this device is capable of incrementing in only one direction, whereas in certain instances it is desirable to have the capability of both opening and closing a joint in precise increments (e.g., selectively reversing directions) during the same diagnostic procedure.
Accordingly, a non-magnetic device is needed by which temporalmandibular joint incrementing in a magnetic resonance imaging procedure can be achieved precisely and simply in either of two opposite directions, without the immediate presence of a physician or technician with the patient, and the primary purpose of the present invention is to provide such a device.